Mobile ladders



Dec. 13, 1966 R.J. MIHALIK 9 9 9 MOBILE LADDERS Filed Aug. 5, 1965 5Sheets-Sheet l iilii ILIIIHHWJIHIHEH III N Will I N VE NTOR.

Dec. 13, 1966 J, MIHALIK 3,291,254

MOBILE LADDERS Filed Aug. 5, 1965 3 SheetsSheet 2 INVENTOR fioeriJMihaZi/o United States Patent 3,291,254 MOBILE LADDERS Robert J.Mihalik, Uniontown, Pa., assignor to Harsco Corporation, New York, N.Y.,a corporation of Delaware Filed Aug. 5, 1965, Ser. No. 477,442 4 Claims.(Cl. 182-15) The present invention relates to mobile ladders. Knowntypes of such ladders include in general a frame mounted on casters, orthe like, and a ladder supported in operative position on and extendingupwardly and rearw-ardly at an angle from a front end portion of theframe. The frame also carries at its front end a pair of spaced legs onebeing arranged adjacent to each of the two casters which support saidfront end when the apparatus is being moved from place to place. Meansare provided for automatically shifting the frame support from saidfront end casters to said legs and thus immobilizing the unit when theoperator mounts the lowermost step, or equivalent element, of the ladderand for restoring the unit to mobile condition by hand or foot actuateddevices. Examples of ladder units of this type are described in U.S.Patent Nos. 2,897,910 and 2,798,652.

A different type of ladder for similar uses is illustrated in my U.S.Patent No. 3,175,641 which discloses a construction wherein a singlecaster mounted at an end portion of the base is actuated to effectivelyshift the ladder assembly into and out of mobile condition.

An object of the present invention has been to provide in the singlecaster type of mobile ladders relatively simple and rugged direct orpositive acting means by which a user may readily shift the caster toinoperative condition and thus in effect immobilize the apparatus bymounting the bottom step of the ladder and may restore said caster tooperative ladder supporting mobile condition by direct positiveoperation of an actuating lever. Although shift ing of the caster to andfrom operative position is effected in the use of my above notedpreviously patented ladder structure, the present invention involvesstructure whereby the shifting, locking and releasing functions areeffected with a substantial reduction in the number of involved partsand wherein said parts operate to produce direct and positive adjustmentof the caster from one condition to another. These features presentcertain advantages as compared to constructions in which such shiftsnecessarily involve spring actuated triggering elements to effectshifting of the caster, locking it in operative position and releasingit in inoperative position.

In general, the present invention may be embodied in a mobile ladderassembly which includes a base having at its front end laterally spacedsupporting legs and, at its rear end, laterally spaced supportingcasters. A mounting step positioned at the front end of the base alsoprovides in effect the actuating .arm of a bell crank fulcrumed in thebase and having a latch arm which extends downwardly from the front endof said actuating arm, said bell crank being biased in a counterclockwise direction. A catch lever is pivoted at its rear end on saidbase and arranged with its front, end extending outwardly between saidsupporting legs; and a swivelling caster is mounted in dependingrelation on said catch lever. A catch bar is carried on said catch leverin position to be in continuous yielding engagement with said latch armof the bellcrank. Said latch arm includes a hook portion having a detentnotch and a lip extending rearwardly beyond the open end of said notchwhich is arranged and adapted to operatively engage said catch bar andthereby releasably lock said caster in operative condition to mobilizethe base when downward pressure is applied against the outer end of saidcatch lever; and said latch arm is disengaged from said catch bar whendownward ice pressure is exerted on the step portion of said bellcran-kthereby releasing the caster unit from load supporting position andshifting the load to said supporting legs.

Other objects and distinctive features of the present invention notabove referred to will appear from the following specification andclaims and from the accompanying drawings wherein is shown a preferredembodiment thereof as described in said specification. The showing somade is not intended to be either exhaustive or as limiting the scope ofthe subject invention. The purpose here is to illustrate the inventionso that others skilled in the art may so fully understand it, itsprinciples and ap plicati-ons, that they may embody it and adapt it inany of various forms appropriate to the attainment of any particular orappropriate purpose in use.

In said drawings:

FIG. 1 is a side and FIG. 2 a front elevation showing the base and partsof the superstructure of a mobile ladder assembly embodying the presentinvention;

FIG. 3, a fragmentary view partly in horizontal section from the line 33of FIG. 2 showing on enlarged scale the location of the caster actuatingand locking mechanism in relation to the mounting step which forms apart thereof and in relation to the front legs of the base;

FIG. 4, a fragmentary view in longitudinal vertical section from theline 4-4 of FIG. 3 and showing the caster unit releasably locked inposition to support the base in mobile condition;

'FIG. 5, a similar view but showing the caster in inoperative positionand the leg ends resting securely on the floor to retain the base inimmobile condition;

FIG. 6, a transverse vertical section from the line 66 of FIG. 4; and

FIG. 7 is a transverse vertical section from the line 7--7 of FIG. 5.

Referring to the drawings, one form of mobile ladder assembly in whichmy invention may advantageously be embodied includes a base or mainframe, indicated generally at 10, on which is mounted a ladder 11extending upwardly at an appropriate angle from the front end of base10. The rear end of said base is conveniently supported on casters 12,one at each rear corner. The front end of said :base is provided withlegs 13 which, when in 'down or operative position, FIGS. 5 and 7,support the front end of base 10 and maintain said base in immobilecondition. And means are provided including a caster 14 whereby saidlegs may be raised from said down posi-' tion and, at the same time,move caster 14 into and releasably lock it in supporting position, asseen in FIGS. 4 and 6, thereby bringing the apparatus into mobilecondition.

A desirably simple and rugged construction for the above indicatedpurposes includes essentially two interacting lever systems andappropriate locking and releasing elements mounted generally at thefront end of base 10.

One of said lever systems incldues a lever arm in the form of a step 15pivotally mounted adjacent to its front edge on a transverse rod 16supported at its ends by means to be described, at the front end of base10, said step 15 being advantageously arranged and adapted to provide ineffect the bottom step of the ladder.

Frame 10 includes rear uprights 17, FIG. 1, connected to front legs 13by horizontal longitudinal braces 18; and said longitudinal braces areconnected by horizontal transverse braces 19, FIG. 3. A sub frameadapted to receive step 15, includes a transverse from bar 20, FIG. 3, atransverse rear angle 21, longitudinal side angles 22, 22 connectingsaid front bar 20 and said rear angle 21, and short upright angles 23interposed between rear angle 21 and transverse brace 19.

As seen more clearly in FIGS. 3 and 4, the ends of pivot rod 16 aresupported in opposed holes in the upright flanges of side angles 22 sothat step 15 rocks in the space defined by bar 20, channel 21 and saidangles 22. Springs 24 are interposed between rear portions of step 15and angle 21, thus normally biasing the rear edge of said step 15 towardnormal, or up, position, FIG. 4.

Referring to FIGS. 3 and 4, step 15 includes a cross brace bar 25 andplates 26 secured thereto in transversely spaced relation, as bywelding, at their inner ends and each having a hole adjacent to itsouter end by which it rotatably engages pivot rod 16. The arrangement issuch that plates 26 rock with step 15. A latch arm 27 is secured at oneend, as by welding, to an outer end portion of each of plates 26. Eachsaid latch arm extends downwardly from the step and is provided at itsbottom or free end with a hook-like terminal wherein a recess 28 openingthrough the inner face of said arm 27 is defined in part by a lip 29extending inwardly beyond said inner face of arm 27 and the open end ofrecess 28.

The parts above described including step 15, plates 26 and latch arms 27constitute in function a lever system or bell crank fulcrumed on rod 16and arranged and adapted to cooperate with another lever system in amanner to control the position of caster 14 and connected parts andthereby to readily adjust the apparatus between mobile and immobileconditions.

As seen in FIGS. 3 and 4, said other lever system includes a footactuated lever, or treadle, conveniently in the form of a yoke shapedlever 30 comprising an outer rounded end and parallel inwardly extendingarms 31. A plate 32 welded to portions of the bottom surfaces of arms 31provides a base on the bottom face of which the caster assembly ismounted to swivel freely.

A hinge tube 33 is welded to an under side surface of angle 21 andsupports the inner ends of said arms 31 of the treadle lever 30. Forthis purpose, each of said inner ends has a tubular collar 34, FIG. 6,of the same internal diameter as that of the hinge tube 33. A hinge pinconveniently in the form of a tube 35 extends through said hinge tube 33and said collars 34 where it is retained by suitable means such as awasher 36 at one end and a cotter pin 37 at the opposite end (left FIGS.6 and 7).

It is noted that the step lever system (step 15, arm or latch 27) isfulcrumed (rod 16) near the front edge of the step frame; whereas thetreadle lever system (30, 31) is fulcrumed or hinged on pin 35 near therear edge of said step frame and at a level below that of the stepfulcrum rod 16. Also, the distance from the hinge axis to the floorcontacting line of caster 14, FIG. 4, is greater than the verticaldistance from said hinge axis to the floor level, FIG. 5. Accordingly,by moving caster 14 from FIG. position to FIG. 4 position, the front endof the base or main frame is lifted thereby raising the bottom ends oflegs 13 off the floor, FIG. 6, to an extent determined by the dilferencebetween said distance from the hinge axis to the floor contacting lineof caster 14 and the vertical distance from said axis to the floorlevel. This dilference is approximately the vertical distance betweenthe floor level and the bottom end of leg 13, FIG. 4.

An embodiment of the present invention also includes means operativelyinterposed between step 15 and lever arms 31 whereby caster 14 carriedby said arms is automatically and releasably locked in operativeposition, FIG. 4, when the outer end of treadle 30 is swung on hinge pin35 downwardly into said FIG. 4 position, as by foot pressure applied byan operator. For this purpose, a catch bar 38, FIG. 3, is secured inposition to cooperate with latches 27 as by welding to upwardly exposedsurface portions of the parallel arms 31.

Free end portions or extensions 39 of bar 38 shown as deflected from thelongitudinal axis thereof at a slight angle, are arranged to operativelyengage inwardly directed edge faces of said latches 27 including thoseof the recesses 28.

In the extreme end position of catch bar 38, FIG. 4,

' rolling movement.

its end portions are engaged in said recesses 28. However, when anoperator mounts on step 15, his weight applied against spring 24 rocksthe latch arms 27 in a clockwise direction and to such an extent as todisengage recess 28 from ends 39 of catch bar 38. As said ends 39 arethus released from locking relation to recess 28, legs 13 drop bygravity into operative base supporting position (immobile condition), asseen in FIGS. 5 and 7; and caster 14 is free to move out of basesupporting position. The change from mobile (FIG. 4) condition toimmobile (FIG. 5) condition obtains as soon as latch 27 disengagesrecesses 28 from the end portions 39 of catch bar 38. In this conditionof the parts, caster 14 may remain in contact with the floor without,however, bearing any Weight other than its own and that of arms 31 andcatch bar 38; or conditions of use may be such that arms 31 of thetreadle are vigorously deflected to the extreme position shown in FIG. 5with the end portions 39 of catch bar resting against upper end portionsof the inwardly exposed faces and lightly clamped against under edgeportions of plates 26. It is noted that when the outer end of thetreadle is swung down from FIG. 5 toward FIG. 4 position, said outerends 39 of catch bar 38 may ride along inner edge face portions of latcharm 27 until they are stopped by lip 29 at which point biasing action ofsprings 24 brings the recesses 28 of said latch arms 27 into lockingengagement with said ends 39.

From the foregoing description and stated mode of operation, it appearsthat apparatus embodying the present invention provides the safetyfeature that, when an operator mounts the bottom step, the caster 14 isautomatically displaced from down or operative mobile position and thelegs move down to support the front end of the base and in effectautomatically lock the apparatus against The base is rendered mobile bydownward pressure of the operators foot on the free end of the catchlever, or treadle.

These advantages are in addition to simplified economical structure andto direct and positive operation of the locking parts. Thus, no springsor equivalent are employed to move the caster into operative position orto retract it therefrom.

The operators weight on the mounting step releases the lock and thefront legs drop by gravity into supporting position, FIG. 5.

In this operation, when the users weight causes latch arm 27 to swingclockwise and thus to disengage notch 28 from catch bar 39, the free endof the treadle or catch lever 39 swings clockwise and catch bar 39 ridesupwardly along latch arm 27. Ordinarily, the application of releasingpressure on the step is momentary so that springs 24 are compressed onlyfor a correspondingly short time. When this pressure is released, aswhen the operators weight is removed from step 15, springs 24 bias latcharm 27 counterclockwise so that the inner edge face of said latch armnow bears yieldingly against catch bar 38, in effect tending to cam itupwardly toward its end position as seen in FIG. 5. Inasmuch as thecatch bar, catch lever and caster are relatively light in weight, thepressure exerted on catch bar 38 by operation of springs 24 issufiicient to retain said parts in their FIG. 5 positions. However, evenif, through slackening of said springs, or otherwise, catch bar 38should slide down toward notch 28, it cannot engage therewith withoutpressure positively applied to the outer end portion of latch lever 30;and caster 14 remains inoperative until it is forced down into its FIG.4 position.

I claim:-

1. In a mobile ladder assembly the combination which includes a basehaving at its front end laterally spaced supporting legs and at its rearend laterally spaced supporting casters, a mounting step constitutingthe actuating arm of a bellcrank fulcrumed at the front end of said baseand normally biased counter-clockwise, said actuating arm having a latcharm extending downwardly from front end portions thereof, a catch leverpivoted at its rear end to said base and positioned with its front endextending forwardly between said front legs, a swivel caster mounted onand depending from an intermediate portion of said catch lever, a catchbar transversely arranged on said catch lever in operative relation tosaid latch arm, said latch arm including a hook portion arranged andadapted to be operatively engaged with and to be disengaged from saidcatch bar whereby, when the rear end portion of the actuating arm of thebellcrank is deflected downwardly by pressure applied on rear portionsof said step, said latch arm is actuated clockwise to disengage saidhook portion thereof from said catch bar and thus free the front end ofsaid catch lever to rock clockwise into inoperative position thereby torelease said legs into base supporting condition and, when the front endof said catch lever is pressed downwardly from said inoperativeposition, said catch bar is returned to operative hook engagingposition, thereby to move said caster to and retain the same inoperative position to support the front end of said base in mobilecondition and to retain said legs in raised non-supporting position.

2. In a mobile ladder assembly wherein a ladder is operatively mountedon a mobile base which has supporting legs at one end and a casteroperatively arranged between said legs and means are provided wherebysaid end of the base can readily be adjusted at will to rest on saidlegs or to rest on said caster, the combination in which said adjustingmeans include a catch lever pivotally mounted on said base andoperatively connected to the caster to move the same and thereby liftsaid legs off a supporting surface while employing the caster as afulcrum, and a bellcrank operatively mounted to rock on said base andoperatively connected to said catch lever and arranged and adapted torelease the caster from said surface engaging position and therebypermit the legs to move to operatively engage said supporting surface,said bellcrank including an actuating arm arranged and adapted to serveas a step for mounting said base and having a latch arm extendingdownwardly from said actuating arm and positioned and adapted to beoperatively engaged with and disengaged from said catch lever.

3. A mobile ladder assembly as defined in claim 2 and wherein said leverincludes a catch bar and said latch arm of the bellcrank includes adetent notch which is engageable with said catch bar to lock the base inmobile condition and is disengageable from said catch bar to bring saidbase into immobile condition.

4. A mobile ladder assembly as defined in claim 3 and wherein saidbellcrank is biased in a direction to retain said latch arm in yieldingengagement with said catch bar.

References Cited by the Examiner UNITED STATES PATENTS 2,798,652 7/1957Easton 18215 2,923,373 2/1960 Ledgerwood 182l7 3,112,010 11/1963 Mihalik182-15 3,155,190 11/1964 Borgman 18215 3,175,641 3/1965 Mihalik 18215'30 REINALDO P. MACHADO, Primary Examiner.

1. IN A MOBILE LADDER ASSEMBLY THE COMBINATION WHICH INCLUDES A BASEHAVING AT ITS FRONT END LATERALLY SPACED SUPPORTING LEGS AND AT ITS REAREND LATERALLY SPACED SUPPORTING CASTERS, MOUNTING STEP CONSTITUTING THEACTUATING ARM OF A BELLCRANK FULCRUMED AT THE FRONT END OF SAID BASE ANDNORMALLY BIASED COUNTER-CLOCKWISE, SAID ACTUATING ARM HAVING A LATCH ARMEXTENDING DOWNWARDLY FROM FRONT END PORTIONS THEREOF, A CATCH LEVERPIVOTED AT ITS REAR END TO SAID BASE AND POSITIONED WITH ITS FRONT ENDEXTENDING FORWARDLY BETWEEN SAID FRONT LEGS, A SWIVEL CASTER MOUNTED ONAND DEPENDING FROM AN INTERMEDIATE PORTION OF SAID CATCH LEVER, A CATCHBAR TRANSVERSELY ARRANGED ON SAID CATCH LEVER IN OPERATIVE RELATION TOSAID LATCH ARM, SAID LATCH ARM INCLUDING A HOOK PORTION ARRANGED ANDADAPTED TO BE OPERATIVELY ENGAGED WITH AND TO BE DISENGAGED FROM SAIDCATCH BAR WHEREBY, WHEN THE REAR END PORTION OF THE ACTUATING ARM OF THEBELLCRANK IS DEFLECTED DOWNWARDLY BY PRESSURE APPLIED ON REAR PORTIONSOF SAID STEP, SAID LATCH ARM IS ACTUATED CLOCKWISE TO DISCENGAGE SAIDHOOK PORTION THEREOF FROM SAID CATCH BAR AND THUS FREE THE FRONT END OFSAID CATCH LEVER TO ROCK CLOCKWISE INTO INOPERATIVE POSITION THEREBY TORELEASE SAID LEGS INTO BASE SUPPORTING CONDITION AND, WHEN THE FRONTWEND OF SAID CATCH LEVER IS PRESSED DOWNWARDLY FROM SAID INOPERATIVEPOSITION, SAID CATCH BAR IS RETURNED TO OPERATIVE HOOK ENGAGINGPOSITION, THEREBY TO MOVE SAID CASTER TO AND RETAIN THE SAME INOPERATIVE POSITION TO SUPPORT THE FRONT END OF SAID BASE IN MOBILECONDITION AND TO RETAIN SAID LEGS IN RAISED NON-SUPPORTING POSITION.